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Operating Modes Section 5-2
I/O Memory I/O memory is the area used for reading and writing from the user program or
a Programming Device. It is comprised of both areas that are cleared when
power is turned OFF and ON, and areas that will retain data.
I/O memory is also partitioned into areas that exchanges data with all Units
and areas strictly for internal use. There are four times at which data can be
exchanged with Units: Once per instruction execution cycle, on the execution
of the I/O refresh instruction IORF(97), input refreshing when an interrupt
input is received, and immediate refresh of outputs on execution of instruc-
tions.
PC Setup
(DM 6600 to DM 6655)
The PC Setup is used to set various initial or other settings through software
switches or parameters. Reading, writing, and comparison can be performed
on this area using a Memory Cassette.
Read-only Area
(DM 6144 to DM 6568)
This area can be read by, but not written from, the user program. A Program-
ming Device must be used to write to this area. If pin 1 on the DIP switch on
the front of the CPU Unit is ON, a Programming Device will also not be able to
write to this area. The data in this area is retained when the power is turned
OFF.
This area includes the Controller Link DM parameter area, the routing table
area, and Serial Communications Board settings area. Reading, writing, and
comparison can be performed on this area using a Memory Cassette.
Error Log (DM 6569 to DM
6599)
The error log stores the times of occurrence and error codes of both fatal and
non-fatal errors that occur in the CPU Unit. Up to 10 errors can be stored.
Expansion Instruction
Information
This area contains the function code allocations for expansion instructions
(instructions for which function codes can be changed or allocated). If pin 4 on
the DIP switch on the front of the CPU Unit is OFF, the default allocations for
the expansion instructions will be used. These allocations cannot be changed
while pin 4 is set to OFF. Reading, writing, and comparison can be performed
on this area using a Memory Cassette.
5-1-2 DIP Switch
The DIP switch is used to set initial or other settings.
5-1-3 Memory Cassette
The user program, data memory (read-only area and PC Setup), and expan-
sion instruction information can be saved using the Memory Cassette. If pin 2
on the DIP switch on the front of the CPU Unit is ON, the data stored in the
Memory Cassette is automatically transferred to the CPU Unit when power is
turned ON.
5-2 Operating Modes
5-2-1 Description of Operating Modes
The following 3 operating modes are available in the CPU Unit. These modes
control the entire user program.
PROGRAM Mode Program execution stops in PROGRAM mode. This mode is used for the fol-
lowing operations:
• Changing PC Setup and other settings.
• Transferring and checking programs.
• Force-setting and resetting bits to check wiring and bit allocation.
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